Simon Flexner

Simon Flexner, (born March 25, 1863, Louisville, Ky., U.S.—died May 2, 1946, New York, N.Y.), American pathologist and bacteriologist who isolated (1899) a common strain (Shigella dysenteriae) of dysentery bacillus and developed a curative serum for cerebrospinal meningitis (1907).

As director of the Rockefeller laboratories (1903–35) and institute (1920–35), Flexner led the research team that was able to produce in monkeys a nonfatal form of poliomyelitis and pass it from monkey to monkey, thus trapping a polio virus for laboratory study.